Here is some good info for you:
(have you taken a vomit sample with you to the vet?)
http://www.dog-pictures.co.uk/dog-ca...vomiting.shtml
Material that is high in mucus tells me that the stomach or high intestine is inflamed. Undigested food can indicate food poisoning, anxiety, or simply over eating. Bile is often present when vomiting is caused by inflammatory bowel disease or pancreatitis. Flecks of bright blood tell me that the stomach is lacerated. If the blood is brown and caramelized I know that the problem is farther down the intestine. Strong digestive odors suggests intestinal obstruction. Bits of aluminum foil, Christmas tree tinsel, Big Mac wrappers, etc. tell me that this is a dietary indiscretion that will be easy to manage. Another important clue is the relationship of vomiting to the pet’s last meal.
Blockages
Anything that blocks the exit from the stomach will eventually cause vomiting.
Two other forms of knotting of the small intestine, volvulus and intussuception also cause vomiting. Volvulus is a spinning round of the intestine causing it to kink. Intussusception is a folding in of the intestine upon itself. In both cases food cannot pass and circulation to that portion of the bowel is interrupted. Some people call this a strangulated intestine. I correct both these problems surgically.
Sudden inflammation of the pancreas causes frequent vomiting.
Ear infections that have migrated to the inner ear affect the organs of balance and can cause vomiting
Sometimes vomiting is the only sign of a tear in the diaphragm. A disrupted diaphragm can be a congenital disease that the pet was born with or it can occur as the result of a car accident. Dogs and cats with this problem tend to vomit shortly after eating. They vomit when portions of the stomach or small intestine become trapped in the tear. X-rays pick up this problem.